1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * Copyright (c) 2013, Google Inc. 4 */ 5 6 #ifndef USE_HOSTCC 7 #include <common.h> 8 #include <fdtdec.h> 9 #include <asm/types.h> 10 #include <asm/byteorder.h> 11 #include <linux/errno.h> 12 #include <asm/types.h> 13 #include <asm/unaligned.h> 14 #include <dm.h> 15 #else 16 #include "fdt_host.h" 17 #include "mkimage.h" 18 #include <fdt_support.h> 19 #endif 20 #include <u-boot/rsa-mod-exp.h> 21 #include <u-boot/rsa.h> 22 23 /* Default public exponent for backward compatibility */ 24 #define RSA_DEFAULT_PUBEXP 65537 25 26 /** 27 * rsa_verify_padding() - Verify RSA message padding is valid 28 * 29 * Verify a RSA message's padding is consistent with PKCS1.5 30 * padding as described in the RSA PKCS#1 v2.1 standard. 31 * 32 * @msg: Padded message 33 * @pad_len: Number of expected padding bytes 34 * @algo: Checksum algo structure having information on DER encoding etc. 35 * @return 0 on success, != 0 on failure 36 */ 37 static int rsa_verify_padding(const uint8_t *msg, const int pad_len, 38 struct checksum_algo *algo) 39 { 40 int ff_len; 41 int ret; 42 43 /* first byte must be 0x00 */ 44 ret = *msg++; 45 /* second byte must be 0x01 */ 46 ret |= *msg++ ^ 0x01; 47 /* next ff_len bytes must be 0xff */ 48 ff_len = pad_len - algo->der_len - 3; 49 ret |= *msg ^ 0xff; 50 ret |= memcmp(msg, msg+1, ff_len-1); 51 msg += ff_len; 52 /* next byte must be 0x00 */ 53 ret |= *msg++; 54 /* next der_len bytes must match der_prefix */ 55 ret |= memcmp(msg, algo->der_prefix, algo->der_len); 56 57 return ret; 58 } 59 60 int padding_pkcs_15_verify(struct image_sign_info *info, 61 uint8_t *msg, int msg_len, 62 const uint8_t *hash, int hash_len) 63 { 64 struct checksum_algo *checksum = info->checksum; 65 int ret, pad_len = msg_len - checksum->checksum_len; 66 67 /* Check pkcs1.5 padding bytes. */ 68 ret = rsa_verify_padding(msg, pad_len, checksum); 69 if (ret) { 70 debug("In RSAVerify(): Padding check failed!\n"); 71 return -EINVAL; 72 } 73 74 /* Check hash. */ 75 if (memcmp((uint8_t *)msg + pad_len, hash, msg_len - pad_len)) { 76 debug("In RSAVerify(): Hash check failed!\n"); 77 return -EACCES; 78 } 79 80 return 0; 81 } 82 83 #ifdef CONFIG_FIT_ENABLE_RSASSA_PSS_SUPPORT 84 static void u32_i2osp(uint32_t val, uint8_t *buf) 85 { 86 buf[0] = (uint8_t)((val >> 24) & 0xff); 87 buf[1] = (uint8_t)((val >> 16) & 0xff); 88 buf[2] = (uint8_t)((val >> 8) & 0xff); 89 buf[3] = (uint8_t)((val >> 0) & 0xff); 90 } 91 92 /** 93 * mask_generation_function1() - generate an octet string 94 * 95 * Generate an octet string used to check rsa signature. 96 * It use an input octet string and a hash function. 97 * 98 * @checksum: A Hash function 99 * @seed: Specifies an input variable octet string 100 * @seed_len: Size of the input octet string 101 * @output: Specifies the output octet string 102 * @output_len: Size of the output octet string 103 * @return 0 if the octet string was correctly generated, others on error 104 */ 105 static int mask_generation_function1(struct checksum_algo *checksum, 106 uint8_t *seed, int seed_len, 107 uint8_t *output, int output_len) 108 { 109 struct image_region region[2]; 110 int ret = 0, i, i_output = 0, region_count = 2; 111 uint32_t counter = 0; 112 uint8_t buf_counter[4], *tmp; 113 int hash_len = checksum->checksum_len; 114 115 memset(output, 0, output_len); 116 117 region[0].data = seed; 118 region[0].size = seed_len; 119 region[1].data = &buf_counter[0]; 120 region[1].size = 4; 121 122 tmp = malloc(hash_len); 123 if (!tmp) { 124 debug("%s: can't allocate array tmp\n", __func__); 125 ret = -ENOMEM; 126 goto out; 127 } 128 129 while (i_output < output_len) { 130 u32_i2osp(counter, &buf_counter[0]); 131 132 ret = checksum->calculate(checksum->name, 133 region, region_count, 134 tmp); 135 if (ret < 0) { 136 debug("%s: Error in checksum calculation\n", __func__); 137 goto out; 138 } 139 140 i = 0; 141 while ((i_output < output_len) && (i < hash_len)) { 142 output[i_output] = tmp[i]; 143 i_output++; 144 i++; 145 } 146 147 counter++; 148 } 149 150 out: 151 free(tmp); 152 153 return ret; 154 } 155 156 static int compute_hash_prime(struct checksum_algo *checksum, 157 uint8_t *pad, int pad_len, 158 uint8_t *hash, int hash_len, 159 uint8_t *salt, int salt_len, 160 uint8_t *hprime) 161 { 162 struct image_region region[3]; 163 int ret, region_count = 3; 164 165 region[0].data = pad; 166 region[0].size = pad_len; 167 region[1].data = hash; 168 region[1].size = hash_len; 169 region[2].data = salt; 170 region[2].size = salt_len; 171 172 ret = checksum->calculate(checksum->name, region, region_count, hprime); 173 if (ret < 0) { 174 debug("%s: Error in checksum calculation\n", __func__); 175 goto out; 176 } 177 178 out: 179 return ret; 180 } 181 182 int padding_pss_verify(struct image_sign_info *info, 183 uint8_t *msg, int msg_len, 184 const uint8_t *hash, int hash_len) 185 { 186 uint8_t *masked_db = NULL; 187 int masked_db_len = msg_len - hash_len - 1; 188 uint8_t *h = NULL, *hprime = NULL; 189 int h_len = hash_len; 190 uint8_t *db_mask = NULL; 191 int db_mask_len = masked_db_len; 192 uint8_t *db = NULL, *salt = NULL; 193 int db_len = masked_db_len, salt_len = msg_len - hash_len - 2; 194 uint8_t pad_zero[8] = { 0 }; 195 int ret, i, leftmost_bits = 1; 196 uint8_t leftmost_mask; 197 struct checksum_algo *checksum = info->checksum; 198 199 /* first, allocate everything */ 200 masked_db = malloc(masked_db_len); 201 h = malloc(h_len); 202 db_mask = malloc(db_mask_len); 203 db = malloc(db_len); 204 salt = malloc(salt_len); 205 hprime = malloc(hash_len); 206 if (!masked_db || !h || !db_mask || !db || !salt || !hprime) { 207 printf("%s: can't allocate some buffer\n", __func__); 208 ret = -ENOMEM; 209 goto out; 210 } 211 212 /* step 4: check if the last byte is 0xbc */ 213 if (msg[msg_len - 1] != 0xbc) { 214 printf("%s: invalid pss padding (0xbc is missing)\n", __func__); 215 ret = -EINVAL; 216 goto out; 217 } 218 219 /* step 5 */ 220 memcpy(masked_db, msg, masked_db_len); 221 memcpy(h, msg + masked_db_len, h_len); 222 223 /* step 6 */ 224 leftmost_mask = (0xff >> (8 - leftmost_bits)) << (8 - leftmost_bits); 225 if (masked_db[0] & leftmost_mask) { 226 printf("%s: invalid pss padding ", __func__); 227 printf("(leftmost bit of maskedDB not zero)\n"); 228 ret = -EINVAL; 229 goto out; 230 } 231 232 /* step 7 */ 233 mask_generation_function1(checksum, h, h_len, db_mask, db_mask_len); 234 235 /* step 8 */ 236 for (i = 0; i < db_len; i++) 237 db[i] = masked_db[i] ^ db_mask[i]; 238 239 /* step 9 */ 240 db[0] &= 0xff >> leftmost_bits; 241 242 /* step 10 */ 243 if (db[0] != 0x01) { 244 printf("%s: invalid pss padding ", __func__); 245 printf("(leftmost byte of db isn't 0x01)\n"); 246 ret = EINVAL; 247 goto out; 248 } 249 250 /* step 11 */ 251 memcpy(salt, &db[1], salt_len); 252 253 /* step 12 & 13 */ 254 compute_hash_prime(checksum, pad_zero, 8, 255 (uint8_t *)hash, hash_len, 256 salt, salt_len, hprime); 257 258 /* step 14 */ 259 ret = memcmp(h, hprime, hash_len); 260 261 out: 262 free(hprime); 263 free(salt); 264 free(db); 265 free(db_mask); 266 free(h); 267 free(masked_db); 268 269 return ret; 270 } 271 #endif 272 273 /** 274 * rsa_verify_key() - Verify a signature against some data using RSA Key 275 * 276 * Verify a RSA PKCS1.5 signature against an expected hash using 277 * the RSA Key properties in prop structure. 278 * 279 * @info: Specifies key and FIT information 280 * @prop: Specifies key 281 * @sig: Signature 282 * @sig_len: Number of bytes in signature 283 * @hash: Pointer to the expected hash 284 * @key_len: Number of bytes in rsa key 285 * @return 0 if verified, -ve on error 286 */ 287 static int rsa_verify_key(struct image_sign_info *info, 288 struct key_prop *prop, const uint8_t *sig, 289 const uint32_t sig_len, const uint8_t *hash, 290 const uint32_t key_len) 291 { 292 int ret; 293 #if !defined(USE_HOSTCC) 294 struct udevice *mod_exp_dev; 295 #endif 296 struct checksum_algo *checksum = info->checksum; 297 struct padding_algo *padding = info->padding; 298 int hash_len = checksum->checksum_len; 299 300 if (!prop || !sig || !hash || !checksum) 301 return -EIO; 302 303 if (sig_len != (prop->num_bits / 8)) { 304 debug("Signature is of incorrect length %d\n", sig_len); 305 return -EINVAL; 306 } 307 308 debug("Checksum algorithm: %s", checksum->name); 309 310 /* Sanity check for stack size */ 311 if (sig_len > RSA_MAX_SIG_BITS / 8) { 312 debug("Signature length %u exceeds maximum %d\n", sig_len, 313 RSA_MAX_SIG_BITS / 8); 314 return -EINVAL; 315 } 316 317 uint8_t buf[sig_len]; 318 319 #if !defined(USE_HOSTCC) 320 ret = uclass_get_device(UCLASS_MOD_EXP, 0, &mod_exp_dev); 321 if (ret) { 322 printf("RSA: Can't find Modular Exp implementation\n"); 323 return -EINVAL; 324 } 325 326 ret = rsa_mod_exp(mod_exp_dev, sig, sig_len, prop, buf); 327 #else 328 ret = rsa_mod_exp_sw(sig, sig_len, prop, buf); 329 #endif 330 if (ret) { 331 debug("Error in Modular exponentation\n"); 332 return ret; 333 } 334 335 ret = padding->verify(info, buf, key_len, hash, hash_len); 336 if (ret) { 337 debug("In RSAVerify(): padding check failed!\n"); 338 return ret; 339 } 340 341 return 0; 342 } 343 344 /** 345 * rsa_verify_with_keynode() - Verify a signature against some data using 346 * information in node with prperties of RSA Key like modulus, exponent etc. 347 * 348 * Parse sign-node and fill a key_prop structure with properties of the 349 * key. Verify a RSA PKCS1.5 signature against an expected hash using 350 * the properties parsed 351 * 352 * @info: Specifies key and FIT information 353 * @hash: Pointer to the expected hash 354 * @sig: Signature 355 * @sig_len: Number of bytes in signature 356 * @node: Node having the RSA Key properties 357 * @return 0 if verified, -ve on error 358 */ 359 static int rsa_verify_with_keynode(struct image_sign_info *info, 360 const void *hash, uint8_t *sig, 361 uint sig_len, int node) 362 { 363 const void *blob = info->fdt_blob; 364 struct key_prop prop; 365 int length; 366 int ret = 0; 367 368 if (node < 0) { 369 debug("%s: Skipping invalid node", __func__); 370 return -EBADF; 371 } 372 373 prop.num_bits = fdtdec_get_int(blob, node, "rsa,num-bits", 0); 374 375 prop.n0inv = fdtdec_get_int(blob, node, "rsa,n0-inverse", 0); 376 377 prop.public_exponent = fdt_getprop(blob, node, "rsa,exponent", &length); 378 if (!prop.public_exponent || length < sizeof(uint64_t)) 379 prop.public_exponent = NULL; 380 381 prop.exp_len = sizeof(uint64_t); 382 383 prop.modulus = fdt_getprop(blob, node, "rsa,modulus", NULL); 384 385 prop.rr = fdt_getprop(blob, node, "rsa,r-squared", NULL); 386 387 if (!prop.num_bits || !prop.modulus) { 388 debug("%s: Missing RSA key info", __func__); 389 return -EFAULT; 390 } 391 392 ret = rsa_verify_key(info, &prop, sig, sig_len, hash, 393 info->crypto->key_len); 394 395 return ret; 396 } 397 398 int rsa_verify(struct image_sign_info *info, 399 const struct image_region region[], int region_count, 400 uint8_t *sig, uint sig_len) 401 { 402 const void *blob = info->fdt_blob; 403 /* Reserve memory for maximum checksum-length */ 404 uint8_t hash[info->crypto->key_len]; 405 int ndepth, noffset; 406 int sig_node, node; 407 char name[100]; 408 int ret; 409 410 /* 411 * Verify that the checksum-length does not exceed the 412 * rsa-signature-length 413 */ 414 if (info->checksum->checksum_len > 415 info->crypto->key_len) { 416 debug("%s: invlaid checksum-algorithm %s for %s\n", 417 __func__, info->checksum->name, info->crypto->name); 418 return -EINVAL; 419 } 420 421 sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME); 422 if (sig_node < 0) { 423 debug("%s: No signature node found\n", __func__); 424 return -ENOENT; 425 } 426 427 /* Calculate checksum with checksum-algorithm */ 428 ret = info->checksum->calculate(info->checksum->name, 429 region, region_count, hash); 430 if (ret < 0) { 431 debug("%s: Error in checksum calculation\n", __func__); 432 return -EINVAL; 433 } 434 435 /* See if we must use a particular key */ 436 if (info->required_keynode != -1) { 437 ret = rsa_verify_with_keynode(info, hash, sig, sig_len, 438 info->required_keynode); 439 if (!ret) 440 return ret; 441 } 442 443 /* Look for a key that matches our hint */ 444 snprintf(name, sizeof(name), "key-%s", info->keyname); 445 node = fdt_subnode_offset(blob, sig_node, name); 446 ret = rsa_verify_with_keynode(info, hash, sig, sig_len, node); 447 if (!ret) 448 return ret; 449 450 /* No luck, so try each of the keys in turn */ 451 for (ndepth = 0, noffset = fdt_next_node(info->fit, sig_node, &ndepth); 452 (noffset >= 0) && (ndepth > 0); 453 noffset = fdt_next_node(info->fit, noffset, &ndepth)) { 454 if (ndepth == 1 && noffset != node) { 455 ret = rsa_verify_with_keynode(info, hash, sig, sig_len, 456 noffset); 457 if (!ret) 458 break; 459 } 460 } 461 462 return ret; 463 } 464